Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$217.86	9.447%	$238.4412	$238.44	$238.45	$238.40
Purchase #2	$125.61	12.666%	$141.5198	$141.52	$141.50	$141.50
Purchase #3	$55.32	5.543%	$58.3864	$58.39	$58.40	$58.40
Purchase #4	$23.30	9.343%	$25.4769	$25.48	$25.50	$25.50
Purchase #5	$65.53	9.651%	$71.8543	$71.85	$71.85	$71.90
Purchase #6	$7.65	3.670%	$7.9308	$7.93	$7.95	$7.90
Purchase #7	$184.58	8.575%	$200.4077	$200.41	$200.40	$200.40
7 purchase totals =	$679.85		$744.0171	$744.02	$744.05	$744.00